Currently there are strict rules to manage audio devices that are not configurable.
Phone speaker is default and then the following will get the audio
There is no device selection option from within Agent-IC (IOS or Android) only on Station-IC.
There maybe a possibility to override the selection by the user by way of creative persistence using the IOS itself but Agent-IC will always try to revert to the automatic selection logic so if you disconnect a device, it will try to resolve it on its own and go back to the system default.
Any modification to hardware or OS is not recommended nor supported by Clear-Com.